Description

METHOD FOR SOLIDIFYING SOLID FOSSIL FUELS AND SOLIDIFIED MATERIALS PREPARED THEREBY

Technical Field

[1] The present invention relates to a method for solidifying solid fossil fuel and a solidified material obtained thereby. More particularly, the present invention relates to a method for solidifying solid fossil fuel, in which a solidified material having excellent durability and high-temperature stability and high heating value can be prepared by adding a solidifying agent, containing straight asphalt as a main component, together with aqueous acrylic resin, to a single solid fossil fuel or mixture thereof, including bituminous coal, powdery coke generated in a process of forming coke into a desired shape, and anthracite coal, as well as a solidified material prepared by said method. Background Art

[2] In a prior process for manufacturing molten iron, which is the basic raw material of steel (hereinafter, referred to as a "furnace process"), a blast furnace is used, and iron ore and coal are used in the blast furnace. However, to spread heat evenly to increase the production rate of molten iron, iron ore has been used as sintered ore in the form of a mass having a given size, prepared through a sintering process, and coal has been used as coke in the form of a mass, prepared through a coke process. However, to carry out such a coke process, a separate coke furnace and a gas system for heating the coke furnace are required, and thus a high equipment cost is incurred and the emission of a large amount of environmental pollutants from such equipment occurs. Also, it is not possible to extinguish the furnace fire in order to reduce production costs, and a lot of time is required for the sintering process and the coke process. In addition, iron ore, which can be used in the sintering process, is limited to expensive mass iron ore, which increases the production cost. Also, coal, which can be used in the coke process, is limited to coking coal, which depends completely on imports and creates the outflow of a large amount of currency, or a mixture containing at least 50-60% coking coal, because the coking coal has high heating value. Moreover, powdery coke, which is generated as a byproduct during the coke process in an amount of about 3-8%, is not easy to reuse in a steel manufacturing process.

[3] In an attempt to solve these problems with the prior furnace process, POSCO Co.,

Korea, developed a new process. According to the new process, powdery iron ore, the price of which is 23% less than that of massive iron ore used in the furnace process or lower, is used, and general bituminous coal, the price of which is 20% less than that of

coking coal or lower, is used as the raw material of coke, and thus the new process has an effect of decreasing production costs by 10-15% compared to the furnace process. This process comprises converting reduced powdery iron ore to sintered ore using an HCI (hot compacted iron) manufacturing system, forming general bituminous coal into coke, and introducing the ore and the coke into a blast furnace to extract molten iron. Unlike the prior furnace process, in the new process, it is possible to extinguish the furnace fire in response to the market and operation time. Thus, the new process allows production to be freely controlled and has an effect of decreasing production costs by about 8%. However, the coal that can be used in the process is still limited to bituminous coal.

[4] In addition, in order to prepare coke using coking coal without carrying out the prior coke process requiring expensive equipment, methods of using materials for solidifying coking coal have been developed. For example, there is a method of using a mixture prepared by mixing petroleum-based pitch, potato starch and molasses in water. However, when this mixture is used as the solidifying agent, the high- temperature stability of the prepared coke is insufficient and the price of the solidifying agent is also high. Thus, this mixture has been limitedly used only in some processes.

[5] Coke, an example of a solid fossil fuel, is used for casting purposes and is also used in metallurgical processes for manufacturing iron alloys, lead and zinc, according to the size and strength thereof, or in furnaces for manufacturing lime and magnesia. Moreover, it is used in the preparation of calcium carbonate, the raw material of acetylene, and coke powder is used as industrial boiler fuel.

[6] Considering the domestic circumstances, where bituminous coal, used as the main raw material of coke, depends entirely on imports, there has been an urgent demand for a method of enabling bituminous coal to be prepared into coke without generating byproducts such as powdery coke, and allows other solid fossil fuels, such as an- thracitic coal and powdery coke, which are domestically produced in large amounts, to be used as raw materials for preparing coke.

[7] According to this demand, the present inventors filed a patent application relating to a composition for solidifying solid fossil fuels, comprising 25-35 wt% of emulsified asphalt, 0.05-0.20 wt% of an emulsifier for asphalt, 0.1-0.3 wt% of hydrochloric acid, 0.01-0.05 wt% of calcium chloride, 0.01-0.05 wt% of oleic acid, 0.005-0.030 wt% of a surfactant, and the balance of water (Korean Patent Application No. 2005-0068731, filed on July 28, 2005). However, this composition has problems in that the production cost of the composition is somewhat high due to the use of emulsified asphalt, and the composition cannot sufficiently handle solid fossil fuels having high moisture content, and thus requires equipment and time for adjusting the moisture content of the solid fossil fuel to a suitable range.

Disclosure of Invention

Technical Problem

[8] The present inventors have found that, when a solidifying agent, which contains, as a main compound, straight asphalt among various petroleum asphalts, and which rapidly solidifies solid fossil fuel, is added together with aqueous acrylic resin to solidify solid fossil fuel, a single solid fossil fuel or mixture thereof, including bituminous coal, anthracite coal and powdery coke, can be used as the raw material for coke, and at the same time, a solidified material of solid fossil fuel, which can maintain the durability and high-temperature stability of a solidified material prepared according to the prior furnace process and has a high heating value, can be prepared without requiring a prior process, which incurs high equipment costs, thereby completing the present invention.

[9] It is an object of the present invention to provide a method for solidifying solid fossil fuel, which enables a high-strength, solidified material to be prepared using any solid fossil fuel as a raw material.

[10] Another object of the present invention is to provide a solidified material prepared from solid fossil fuel by said method. Technical Solution

[11] To achieve the above objects, according to one aspect of the present invention, there is provided a method for solidifying solid fossil fuel using a solidifying agent, the method comprising the steps of: (1) mixing at least one solid fossil fuel with 5-8 parts by weight, based on 100 parts by weight of the solid fossil fuel, of a solidifying agent, and 1-4 parts by weight, based on 100 parts by weight of the solidifying agent, of aqueous acrylic resin; (2) shaping the mixture prepared in the step (1); and heating the shaped material prepared in the step (2), at a temperature of 150-200 ⁰ C, to prepare a solidified material, wherein the solidifying agent contains, based on the total weight of the solidifying agent, 34-52 wt% of straight asphalt, 0.1-0.3 wt% of an emulsifier for asphalt, 0.2-0.4 wt% of hydrochloric acid, 0.03-0.05 wt% of calcium chloride, and the balance of water.

[12] In another aspect of the present invention, there is provided a solidified material of solid fossil fuel, which is prepared by mixing at least one solid fossil fuel with 5-8 parts by weight, based on 100 parts by weight of the solid fossil fuel, of a solidifying agent, and 1-4 parts by weight, based on 100 parts by weight of the solidifying agent, of aqueous acrylic resin, wherein the solidifying agent contains, based on the total weight of the solidifying agent, 34-52 wt% of straight asphalt, 0.1-0.3 wt% of an emulsifier for asphalt, 0.2-0.4 wt% of hydrochloric acid, 0.03-0.05 wt% of calcium chloride, and the balance of water.

Advantageous Effects

[13] The solidifying method according to the present invention uses the solidifying agent for rapidly solidifying solid fossil fuels along with aqueous acrylic resin. According to the inventive solidifying method, a solidified material, which can maintain the durability and high-temperature durability of a prior solidified material prepared using only coking coal as a raw material and has high heating value, can be prepared using, as a raw material, a single solid fossil fuel or mixture thereof, including bituminous coal, anthracite coal and powdery coke. Also, because aqueous acrylic resin is used, the solidified material prepared according to the inventive method can exhibit high strength at low cost compared to the prior solidified material.

[14] In addition, the inventive solidifying method can be carried out in an existing factory or a simple factory constructed without complicated unnecessary facilities. Best Mode for Carrying Out the Invention

[15] Hereinafter, the present invention will be described in further detail.

[16] In the present invention, a solidified material of solid fossil fuel is prepared by mixing a solid fossil fuel with a solidifying agent serving as a binder, which facilitates the solidification of the solid fossil fuel, and aqueous acrylic resin serving as a reinforcing agent. However, if a single kind of bituminous coal material is used as solid fossil fuel, cement is additionally added to prepare a solidified solid fossil fuel material.

[17] In the present invention, the term solid fossil fuels is intended to exclude liquid and gaseous fossil fuels, such as petroleum and natural gas, among fossil fuels. As the solid fossil fuel, coal itself or coal-based fuel can be used without any particular limitation. Particularly, it is most preferable to use powdery coke, bituminous coal, anthracite coal, or a mixture of two or more thereof.

[18] Meanwhile, the solidifying agent serves to change solid fossil fuel from a powdery form to a massive form, and contains straight asphalt, an emulsifier for asphalt, hydrochloric acid, calcium chloride and water.

[19] Generally, petroleum asphalts are obtained in production processes of petroleum- based products, such as petroleum refining, and can be divided into straight asphalt, asphalt cement, cutback asphalt, emulsified asphalt, blown asphalt, modified asphalt and the like. Among them, the straight asphalt is the heaviest fraction contained in crude oil and is residue obtained by completely removing light fractions by distillation in a high vacuum through a vacuum distillation system. It has high elongation and adhesion, and the softening point thereof is generally lower than 65 ⁰ C. It is used mainly for road pavement and airport pavement. Such straight asphalt is commercially available under the trade names of AP-3, AP-5, etc. from asphalt production

companies in Korea, and thus it can be used without any additional processing to reduce production costs. In the present invention, the straight asphalt serves to increase the elasticity and stability of mixed particles and waterproof surfaces. If it is contained in an amount of less than 34 wt%, the high-temperature stability of the solidifying agent will be insufficient due to a reduction in the elasticity between particles, and if it is contained in an amount of more than 52 wt%, the solidifying agent will burn too rapidly or reduce the porosity of fossil fuels. For this reason, the straight asphalt is contained in an amount of 34-52 wt% based on the total weight of the solidifying agent.

[20] The emulsifier for asphalt has good degradability due to its high emulsifying ability, and is used to emulsify asphalt. As the emulsifier, any emulsifier can be used without any particular limitation as long as it is a cationic or non-ionic emulsifier. If it is contained in an amount of less than 0.1 wt%, it will not emulsify asphalt, and if it is contained in an amount of more than 0.3 wt%, it will enhance adhesion, but increase the product cost. For this reason, the emulsifier is contained in an amount of 0.1-0.3 wt% based on the total weight of the solidifying agent.

[21] Hydrochloric acid is mixed with the emulsifier for asphalt to perform dispersion and decomposition, and is used for mixing and purification. Also, due to the hydrogen ion (H ) of hydrochloric acid, the solidifying agent becomes cationic, making it possible to rapidly solidify solid fossil fuels. If it is contained in an amount of less than 0.2 wt%, it will not provide smooth dispersion and decomposition, and if it is contained in an amount of more than 0.4 wt%, it will cause an environmental problem. For this reason, hydrochloric acid is contained in an amount of 0.2-0.4 wt% based on the total weight of the solidifying agent. More preferably, it is contained in an amount of 0.30-0.35 wt%.

[22] Calcium chloride functions to prevent freezing and is used to increase density so as to prevent cracks and promote absorption. If it is contained in an amount of less than 0.03 wt%, it will not sufficiently absorb moisture, and thus will has an insufficient effect on the prevention of freezing, and if is contained in an amount of 0.05 wt%, a large amount of anhydrides will be generated, making it difficult to maintain the solidifying agent in the liquid state. For this reason, it is contained in an amount of 0.03-0.05 wt% based on the total weight of the solidifying agent.

[23] Water is contained to form the rest of the above-described components, and the content thereof is adjusted according to the kind and wettability of product. If water is contained in an excessively low amount, emulsification and dispersion will not sufficiently occur, and the cost of the solidifying agent will increase, and if it is contained in an excess amount, it will reduce the adhesion between particles, waterproofing ability, and strength of the solidifying agent. For this reason, the content of water

should also be adjusted in a suitable range. Most preferably, it is contained in an amount of about 50-60 wt% based on the total weight of the solidifying agent.

[24] In addition, to further increase the adhesion between particles, the solidifying agent may comprise an acrylic emulsion-based asphalt modifier in an amount of 1-3 wt% based on the total weight of the solidifying agent. Preferably, the modifier is a styrene- butadiene-styrene (SBS) block copolymer. For example, Butonal NS 198 (manufactured by BASF, USA) can be used.

[25] The solidifying agent prepared according to the above-described composition is a liquid emulsion containing water, in which hardly any separation between components occurs. Moreover, it is easily uniformly mixed with solid fossil fuels, so that the strength variation of the products is very low, making process and quality control easier. Furthermore, since the liquid phase of the solidifying agent is almost burned out in a curing process during the production of solidified products, the produced solidified material does not increase the amount of ash even when it is used as fuel and a reducing agent. Thus, it will generate little or no additional slag in steel manufacturing operations. However, if the liquid-phase solidifying agent is used in an amount of less than 5 parts by weight based on 100 parts by weight of solid fossil fuel, there will be a problem in the solidification and strength of solid fossil fuel, and if it is used in an amount of more than 8 parts by weight, it will reduce the porosity of the resulting solidified material, thus reducing the heating value and burning properties of the solidified material and increasing the product cost. For this reason, it is preferably used in an amount of 5-8 parts by weight. More preferably, it is used in an amount of 6-7 parts by weight.

[26] Meanwhile, the aqueous acrylic resin, used as a reinforcing agent, serves to increase the adhesion between particles and improve waterproofing ability because it is a resin component. Thus, the aqueous acrylic resin makes it possible to prepare a product having greatly increased adhesion, fine particle dispersion and waterproofing properties. Also, it has excellent high-temperature stability, and thus makes it possible to prepare a product which can be burned for a long time. If the aqueous acrylic resin is contained in an amount of less than 1 part by weight based on 100 parts by weight of the solidifying agent, it will provide reduced adhesive and waterproofing properties, and if it is contained in an amount of more than 4 parts by weight, it will increase the product cost and limit the chemical efficacy of other components. For this reason, the aqueous acrylic resin is contained in an amount of 1-4 parts by weight based on 100 parts by weight of the solidifying agent. As the aqueous acrylic resin, any material can be used without any particular limitation as long as it performs the above functions. For example, an aqueous acryl having a liquid content of more than 45% can be used. When this aqueous acrylic resin is used as one component of the solidifying agent,

there will be a problem in that the asphalt component is early solidified. For this reason, the aqueous acrylic resin as a reinforcing agent is added to solid fossil fuel separately from the solidifying agent.

[27] Meanwhile, when a solidified material is prepared using a single material of bituminous coal as a solid fossil fuel, cement is further added in the step of mixing the solidifying agent and the like. Any cement can be used without any particular limitation thereon, as long as it is a conventional Portland cement. If the cement is contained in an amount of less than 1 part by weight based on 100 parts by weight of the bituminous coal, it cannot compensate for the property of a solidified material of bituminous coal, which has poor high-temperature stability, and if it is contained in an amount of more than 3 parts by weight, the heating value of the solidified material will be reduced, and the emission of carbon dioxide from the solidified material will be insufficient, causing a problem of reduction in a steel manufacturing process. For this reason, the cement is preferably contained in an amount of 1-3 parts by weight based on 100 parts by weight of bituminous coal.

[28] When the solid fossil fuel, the solidifying agent and the aqueous acrylic resin are prepared according to the above-described components and contents, a solidified material such as coke can be prepared by mixing the above components with each other, shaping the mixture using a shaping machine according to a conventional method, and heating the shaped material at a temperature of 150-200 ⁰ C. However, if a single material of bituminous coal is used as solid fossil fuel, cement, in addition to the above components, is further added in the mixing step, and solidified material can be prepared in the same manner as described above.

[29] When a solidified material is prepared according to the above-described solidifying method, solid fossil fuel as a raw material can be solidified regardless of the moisture content thereof, curing time is reduced, thus increasing the production rate of the solidified material, and it is possible to prepare products having excellent durability and high-temperature stability. Also, it is possible to prepare a product having greatly increased adhesion, fine particle dispersion and waterproofing properties. Furthermore, the heating value of coke, prepared using a single bituminous coal, anthracite coal and powdery coke or mixture thereof, according to each of the conventional furnace process and the inventive method, was measured. As a result, it was seen that the heating value of the coke prepared according to the conventional furnace process was about 5,130-7,717 kcal/D, and that the heating value of the coke prepared according to the inventive method showed an increase of about 10% compared to the coke prepared according to the prior furnace process.

[30] Hereinafter, the preparation of a solidifying agent will first be described, and the present invention will then be described in further detail with reference to examples

and comparative examples. It is to be understood, however, that these examples are illustrative only, and the scope of the present invention is not limited thereto.

[31] Preparation Examples 1 to 3: Solidifying agents [32] Straight asphalt (AP-3; manufactured by SK Corporation, Korea) or emulsified asphalt (AP-3; manufactured by SK Corporation, Korea) was stored in a separate storage tank at a temperature higher than 130 ⁰ C. In another storage tank, a mixture containing quantified amounts of an emulsifier for asphalt (Farmin ST-7; Kao Corp., Japan), hydrochloric acid, calcium chloride and water was stored at a temperature of 80 ⁰ C. The asphalt and the mixture were placed and emulsified in a homogenizer, thus preparing solidifying agent of Preparation Examples. Herein, each of the components was added in an amount shown in Table 1 below.

[33] Table 1

[34] Examples 1 to 3 and Comparative Examples 1 to 4: Preparation of coke [35] The solidifying agents according to the components and contents of Table 1 were prepared in advance. Powdery coke was fed into a feed hopper disposed at a conventional equipment line for coke formation and transferred to a storage hopper, in which it was weighed. The powdery coke, the previously prepared solidifying agent, and aqueous acrylic resin as a reinforcing agent, were mixed with each other in a tube mixer. Then, the mixture was formed into a given shape in a conventional shaping machine at a pressure of 5 kg/D, and the raw material coal was discharged from the machine. Then, the raw material coal was transferred to a stabilization apparatus, in which it was heated at a temperature of 180 ⁰ C for 30 minutes, thus producing shaped coke. Herein, each of the components was added in an amount shown in Table 2 below. Also, the reinforcing agent was added in an amount of 2.5 parts by weight based on 100 parts by weight of the solidifying agent.

[36] Table 2

[37] [38] Test Example 1: Measurement of coke quality [39] The coke prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was measured for initial weight moisture (IM), volatile matter (VM; dry basis), ash and fixed carbon (FC) contents, compressive strength, porosity and heating value according to conventional methods. The measurement results are shown in Table 3 below.

[40] Table 3

[41] Coke prepared according to the conventional furnace process using coking coal as a raw material contains 0.5-2.0 wt% of volatile matter, 10-13 wt% of ash and 80-89 wt% of fixed carbon and has a heating value of 6,500-7,200 kcal/D, a compressive strength

of 50-60 kgf/D and a porosity of 30-45%. In comparison with this, the contents of the main components of the coke, prepared in Examples 1-3 by adding the inventive solidifying agent to powdery coke as a raw material, were similar to those of the prior coke, and the heating values thereof were also similar to that of the prior coke. Meanwhile, the coke prepared in Comparative Examples 1-4 was generally inferior to that of Examples 1-3 with respect to compressive strength, porosity and heating values, and would be unsuitable as a substitute for the conventional coke prepared using coking coal as a raw material.

[42] Examples 4 to 8: Preparation of coke [43] According to the components and contents shown in Table 4 below, a solidifying agent, aqueous acrylic resin, cement and a single solid fossil fuel or mixture thereof were uniformly mixed with each other in the same manner as in Examples 1-3, thus producing coke. In Example 8, cement (manufactured by Tong Yang Cement Corp, Korea) was added in the mixing step.

[44] Table 4

[45] Test Example 2: Measurement of coke quality [46] The main component contents and heating values of the cokes prepared in Examples 4-8 were measured, and the measurement results are s2hown in Table 5 below.

[47] Table 5

[48] The coke prepared in Example 8 using only bituminous coal as a raw material and having the inventive solidifying agent added thereto had the highest heating value. In addition, the cokes prepared in Examples 5 and 6 using either powdery coke or a mixture of anthracite coal and bituminous coal as a raw material, and the coke prepared in Example 4 using a mixture of powdery coke and anthracite coal without using bituminous coal, also showed an excellent heating value of more than 6,500 kcal/D. Meanwhile, the coke prepared in Example 7, using only anthracite coal as a raw material, had a heating value of more than 6,200 kcal/D, which is a greatly increased value in view of the fact that the heating value of anthracite coal is generally in the range of 4,500-5,800 kcal/D.

[49] Test Example 3: High-temperature stability test of coke

[50] Each of a sample coal formed from the coke of Example 6, and a sample coal

(manufactured by POSCO Co.) formed from the coke produced in an existing coke process, was adjusted to a temperature of 1,152 ⁰ C in a conventional high-temperature stability test apparatus. Then, the state of coke was observed after 1 hour and 30 min, after 30 minutes at 1152 ⁰ C, and after 30 minutes at 770 ⁰ C. As a result, the sample coal according to the existing process was severely deformed, whereas the sample coal prepared by adding the inventive solidifying agent was not deformed even at high temperatures.

[51] Test Example 4: Durability test of coke

[52] The shaped coke material of Example 1 was placed in a conventional electric furnace, in which the external behavior of the coke was observed at temperatures of 1,000 ⁰ C and 1,200 ⁰ C. As a result, the coke prepared in Example 1 by adding the inventive solidifying agent maintained the original structure thereof even at a high temperature of 1200 ⁰ C without showing product degradation phenomena such as fractures and cracks. Thus, it can be expected that there will be no behavior preventing aeration in the furnace due to degradation.

[53] The solidifying method of the present invention can be carried out on an existing equipment line for coke formation. Alternatively, it can also be carried out in an equipment line constructed to include minimal facilities, such as a mixer for mixing

fossil fuel with the solidifying agent and the like, a forming machine for forming the mixture into a desired shape, and a stabilization apparatus for heating the shaped material in a pretreatment process prior to use as a product, obviating complex unnecessary facilities.

[54] Mixed shaped coal, which is prepared by mixing two or more solid fossil fuels with each other, can be produced as a custom product satisfying various demands of consumers by adjusting heating value and combustion time, and can be formed into various shapes. Because the strength of the product can be controlled freely in the range of 30-80 D/D, the quality of the product can be controlled according to the demands of consumers. Also, the size of the product can be controlled in the range of 25-200D, and the product can also be prepared to have various shapes. Industrial Applicability

[55] The solidified material prepared according to the solidifying method of the present invention can be widely used in iron mills, steel works, steam power plants, co- generation power plants, cement manufacture's kilns, glass manufacturing plants, nonferrous metal manufacturing plants, iron foundries, tire factories, fuel for controlled agriculture, home fuel, incineration plants and the like.

[56] In the present invention, only cokes were prepared as examples of solidified materials, but the scope of the present invention is not limited thereto. The solidified materials according to the present invention include all solidified materials prepared using solid fossil fuel, the inventive solidifying agent for solidifying the solid fossil fuel, and aqueous acrylic resin.

[57]